Boats, ships and related vessels have to be aligned with the lock of a canal to pass through the lock. Usually, a concrete wing, wall or related structure of 1000 to 2000 feet is constructed at the entrance to the lock as a means to align the vessel with the lock. The pilot of the vessel points the vessel against this wing and allows it to slide along the wing until it enters into the lock. Hence, the vessel becomes aligned with the lock by sliding along the wing.
Since the vessel generates immense forces upon contact with wing or wall, it is customary to supply a bumper either on the vessel or on the wing or wall. Timber has been used as the rub strip bumper in most instances as it offered good slip properties, but unfortunately timber does not readily absorb or dissipate the impact force of the vessel contacting the wing or wall. Therefore, these forces are transmitted back into the lock or into the hull of the ship and could possibly result in damage to either or both. Also, the timber disintegrates under these forces and has to be replaced rather frequently.